1.. BSD LICENSE 2 Copyright(c) 2010-2014 Intel Corporation. All rights reserved. 3 All rights reserved. 4 5 Redistribution and use in source and binary forms, with or without 6 modification, are permitted provided that the following conditions 7 are met: 8 9 * Redistributions of source code must retain the above copyright 10 notice, this list of conditions and the following disclaimer. 11 * Redistributions in binary form must reproduce the above copyright 12 notice, this list of conditions and the following disclaimer in 13 the documentation and/or other materials provided with the 14 distribution. 15 * Neither the name of Intel Corporation nor the names of its 16 contributors may be used to endorse or promote products derived 17 from this software without specific prior written permission. 18 19 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 22 A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 23 OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 24 SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 25 LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 29 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 31Profile Your Application 32======================== 33 34The following sections describe methods of profiling DPDK applications on 35different architectures. 36 37 38Profiling on x86 39---------------- 40 41Intel processors provide performance counters to monitor events. 42Some tools provided by Intel, such as VTune, can be used to profile and benchmark an application. 43See the *VTune Performance Analyzer Essentials* publication from Intel Press for more information. 44 45For a DPDK application, this can be done in a Linux* application environment only. 46 47The main situations that should be monitored through event counters are: 48 49* Cache misses 50 51* Branch mis-predicts 52 53* DTLB misses 54 55* Long latency instructions and exceptions 56 57Refer to the 58`Intel Performance Analysis Guide <http://software.intel.com/sites/products/collateral/hpc/vtune/performance_analysis_guide.pdf>`_ 59for details about application profiling. 60 61 62Profiling on ARM64 63------------------ 64 65Using Linux perf 66~~~~~~~~~~~~~~~~ 67 68The ARM64 architecture provide performance counters to monitor events. The 69Linux ``perf`` tool can be used to profile and benchmark an application. In 70addition to the standard events, ``perf`` can be used to profile arm64 71specific PMU (Performance Monitor Unit) events through raw events (``-e`` 72``-rXX``). 73 74For more derails refer to the 75`ARM64 specific PMU events enumeration <http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.100095_0002_04_en/way1382543438508.html>`_. 76 77 78High-resolution cycle counter 79~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 80 81The default ``cntvct_el0`` based ``rte_rdtsc()`` provides a portable means to 82get a wall clock counter in user space. Typically it runs at <= 100MHz. 83 84The alternative method to enable ``rte_rdtsc()`` for a high resolution wall 85clock counter is through the armv8 PMU subsystem. The PMU cycle counter runs 86at CPU frequency. However, access to the PMU cycle counter from user space is 87not enabled by default in the arm64 linux kernel. It is possible to enable 88cycle counter for user space access by configuring the PMU from the privileged 89mode (kernel space). 90 91By default the ``rte_rdtsc()`` implementation uses a portable ``cntvct_el0`` 92scheme. Application can choose the PMU based implementation with 93``CONFIG_RTE_ARM_EAL_RDTSC_USE_PMU``. 94 95The example below shows the steps to configure the PMU based cycle counter on 96an armv8 machine. 97 98.. code-block:: console 99 100 git clone https://github.com/jerinjacobk/armv8_pmu_cycle_counter_el0 101 cd armv8_pmu_cycle_counter_el0 102 make 103 sudo insmod pmu_el0_cycle_counter.ko 104 cd $DPDK_DIR 105 make config T=arm64-armv8a-linuxapp-gcc 106 echo "CONFIG_RTE_ARM_EAL_RDTSC_USE_PMU=y" >> build/.config 107 make 108 109.. warning:: 110 111 The PMU based scheme is useful for high accuracy performance profiling with 112 ``rte_rdtsc()``. However, this method can not be used in conjunction with 113 Linux userspace profiling tools like ``perf`` as this scheme alters the PMU 114 registers state. 115